If you're here, you're probably dealing with a commercial HVAC system—specifically a McQuay chiller—and have run into a question about maintenance, support, or a weird error code. I get it. I manage equipment ordering and vendor coordination for a mid-sized company, and I've learned a lot the hard way since I took over purchasing in 2020. This FAQ covers the stuff I wish someone had told me, from tech support numbers to that annoying Nest thermostat reset.
Full disclosure: This advice is based on my experience as an admin buyer, not an HVAC engineer. Always verify current contacts and regulations.
1. What's the quickest way to get McQuay chiller tech support?
If you need immediate help, picking up the phone is still the fastest route. I've found that calling their technical service line directly gets you to a human faster than email. The number you want is usually linked from the Daikin Applied website (since they own McQuay now). As of early 2025, the main support line is [Daikin Applied Technical Support - Note to editor: Verify current phone number].
Pro tip from someone who's been on hold too many times: Have your chiller model number and serial number ready. They're usually on a metal nameplate on the side of the unit. Without those, the support agent can't look up the build sheet, and you'll waste time going back and forth. I once spent 20 minutes trying to explain a 'COP Arrest' code without the model number—don't be like me.
For less urgent stuff, the Daikin Applied portal has a parts and service section where you can submit a ticket. But for a chiller that's down, call.
2. My chiller is showing a 'COP Arrest' alarm—what does that mean?
This one scared me the first time I saw it. 'COP' stands for Coefficient of Performance, and an 'Arrest' basically means the chiller's controls shut it down because the performance dropped below a safe threshold. It's a protective measure, not a sign the unit is destroyed. The most common cause is a refrigerant issue—either low charge, a leak, or a problem with the expansion valve.
What you shouldn't do is just clear the alarm and restart it. I've seen teams try that, and the chiller just trips again. You need actual tech support to run diagnostics. Check the suction pressure and discharge temperature readings on the controller. If they're out of range, you've found your problem. This was accurate as of my 2023 training on McQuay chillers; refrigerant handling regs change, so verify current standards with your service contractor.
3. Where can I find reliable McQuay HVAC parts?
Parts availability is a big deal in commercial HVAC. For genuine McQuay parts, your best bet is an authorized Daikin Applied distributor. They can cross-reference the part number. If you're in a pinch, there are also specialized online parts suppliers like Trane Parts (they sell some McQuay-compatible stuff) and HVAC Parts Outlet, but I'd verify compatibility carefully.
I learned this the hard way: after the third late delivery from a non-authorized vendor, I was ready to give up on them entirely. What finally helped was building in a buffer for lead times and sticking with the distributor for critical like-for-like replacements. One of my biggest regrets from 2021: not checking the warranty status of a used compressor before ordering it. Cost me $1,200 in restocking fees.
4. My AC compressor is short-cycling. Is this a McQuay-specific issue?
No, short-cycling (the compressor turning on and off rapidly) can happen on any brand, from a residential Trane to a massive centrifugal chiller. But the troubleshooting steps are similar. On a commercial unit, the most common causes are:
- Low refrigerant charge: A leak causes the pressure safety switch to trip.
- Dirty condenser coils: Reduces heat transfer, causing high-head pressure trips.
- Faulty control board: Sometimes a sensor reads bad data.
- A bad thermostat or sensor: Telling the system the space is too cold when it isn't.
Don't just keep resetting it—that wears the compressor down fast. You need a tech to measure superheat and subcooling to pinpoint the issue. This is the kind of thing where calling a local service provider is smarter than trying to fix it yourself.
5. How do I reset a Nest thermostat if my HVAC is acting weird?
I know, a Nest thermostat sounds like a residential thing, but I've seen them in small commercial offices and break rooms. If your system is misbehaving after a power outage or a configuration change, a reset can help.
To do a restart (doesn't lose settings): Go to Settings on the thermostat → Reset → Restart.
To do a factory reset (wipes all settings and Wi-Fi): Go to Settings → Reset → Factory Reset.
Important: After a factory reset, you'll need to re-setup the thermostat through the app. Also, check the 'Equipment' settings in the menu to make sure it's configured for your specific system (e.g., conventional vs. heat pump). A wrong configuration can cause short-cycling or weird fan behavior. This info is from my own setup in 2022; the Nest software updates, so the exact menu path might vary—check the Google Home app for the latest instructions.
6. What's the deal with 'Woozoo fan'—does it relate to commercial HVAC?
Not really. Woozoo is a brand of personal desk fans by Iris Ohyama, popular in Japan. They're not made for commercial HVAC. That said, they're surprisingly good for spot cooling in small offices. I bought one for my desk in 2023. It's quiet and moves a lot of air. But if you're trying to fix a chiller, looking for 'Woozoo' info won't help. Believe me, I've made that search mistake out of desperation.
7. What's the first thing I should do when a McQuay chiller alarm goes off?
Don't panic. The control panel logs the trip history. Navigate to the alarm or trip log—usually under a 'History' menu. Note the exact alarm code (like 'Low Evaporator Pressure' or 'Anti-Recycle Timer'). Then, safely check the obvious stuff before calling tech support: Is the power on to the unit? Is the chilled water pump running? Are the condenser fans spinning freely? You'd be surprised how often a tripped breaker or a locked-out pump is the real culprit.
A quick checklist I use:
- Note the exact alarm code from the controller.
- Check the disconnect switch and breaker panel.
- Verify the chilled water and condenser water pumps are running.
- Check for any obvious leaks (puddles of water around the unit, oil stains).
- Call tech support with the model, serial, and alarm code.
I still kick myself for not taking a photo of the alarm screen the first time. If I'd sent it to the support agent, they could've diagnosed it in five minutes instead of forty.
Pricing Note: Parts and service quotes change fast. What I paid for a replacement control board in Q4 2024 ($2,400 including labor) might be different now. Always verify current rates with your service provider before approving work.
